1. Field of the Invention
The present invention relates to auxiliary powered units for assisting vehicles in moving load trailers. In particular, the present invention relates to an apparatus for reversing the functions of the control sensors for the engine and brakes of a powered trailer in relation to the directions of movement of the powered trailer.
2. Description of the Prior Art
Increased concerns about efficient energy consumption have led to the production of smaller and lighter automobiles. Such vehicles attain greater fuel efficiencies than previous models by having smaller engines, smaller bodies and many components made of lightweight materials. Because these lighter vehicles have smaller engines, their ability to pull trailers of any substantial load is greatly diminished. In addition, because such vehicles are so lightweight, substantial stress is created on a vehicle's frame when a heavy trailer is hitched thereto. Therefore, when a trailer of substantial load is to be moved by a small automobile, a booster source of power with means for preventing the weight of the trailer from being transferred completely onto the automobile frame is desired.
A powered trailer suitable for addressing these concerns is shown in U.S. Pat. Nos. 4,475,612 and 4,502,557, which are incorporated by reference herein. These patents show a powered trailer for aiding a vehicle in moving a load trailer. The powered trailer has a tongue assembly between the powered trailer and vehicle which prevents transfer of a substantial amount of tongue weight of the powered trailer to the vehicle and which has an apparatus for controlling the speed of the powered trailer dependent upon the position and motion of the vehicle relative to the powered trailer.
The powered trailer shown in these patents employs a two-part tongue assembly, with a first part thereof being attached to the vehicle and a second part thereof being attached to the powered trailer. Movement of the vehicle relative to the powered trailer moves the first part of the tongue assembly slidably relative to the second part. This movement is detected by the piston arm portions of a pair of opposed hydraulic actuators. One of these actuators is operably connected to the engine of the powered trailer, while the other is operably connected to the brake system of the powered trailer. The engine and brake system of the powered trailer are thus operated as a function of movement of the first and second members of the tongue assembly relative to one another.
The actuators are connected to the engine (via its carburetor) and brake systems of the powered trailer by hydraulic fluid lines. To allow the engine and brakes of the powered trailer to operate when the vehicle and powered trailer are moved in "reverse" (by placing the powered trailer in a reverse mode for transmission purposes), a four-way valve is provided in the hydraulic lines mentioned above to reverse the operable connections between the hydraulic actuators and the engine and brake system of the powered trailer. Thus, the hydraulic actuator that operates the carburetor of the engine when the powered trailer is in a mode for forward movement is changed, via the valve, to operate the brake system. Similarly, the hydraulic actuator which is operably connected to the brake system when the powered trailer is in a mode for forward movement is changed, by the valve, to operate the carburetor of the engine.
This system has been found impractical and unworkable through practice. The use of a valve which alternatively connects and disconnects hydraulic lines has been found to be an inefficient means for reversing the functions of the drive and braking systems of a powered trailer. Most notably is a problem which arises when the valve is operated to reverse these systems when the brakes are being applied or when the powered trailer is in a state of acceleration. Because hydraulic lines are involved, it is possible that the brake system will become stuck in a preloaded position or that the accelerator will be stuck in a preloaded position relative to normally desired hydraulic amplitudes for those systems. To this end, it is thus desirable to provide a more suitable means for reversing the functions of the engine acceleration and braking systems on a powered trailer which overcomes this inherent disadvantage of the prior art devices.